Since you have a 1-year cliff and have only been there 11 months, sounds like as of today you have 0% equity. So the immediate question may be whether your co-founder can fire you.

In 1 month, you've vested 25% of your grant, or 10% of the company. So I would try to get to that mark to strengthen your negotiating position. Any references to 40% are red herrings at this point.

Unless there's a specific buyback clause in your stakeholder agreement, they're under no obligation to buy you out at any time. (They may have the right to do so. That's not uncommon.)

Of course, you're under no obligation to resign, either. So this is a negotiation.

So the way I see it, you have a few options:

1. You take your 10% and leave. You "don't want any equity", but better something you don't want than nothing.

2. You agree to a buyback, potentially at a discount to FMV. If you don't know what FMV is, it's hard to negotiate one way or another. It's v. likely not $1M. Sounds like this is a no-go.

2B. You agree to a non-cash buyback, e.g., in IP. You spent 11 months building the tech: what if you took that with you?

3. You flip the script and buy your co-founder out.

In any case, your relationship is over. You might walk away with nothing.